I have a theory that his family was abusive and he learned to distrust strangers and became convinced that he needed to always stand on his own two feet because nobody would ever truly have his back. I've been through a similar phase in my life caused by neglect and abuse throughout my childhood and adolescence. Could be totally wrong ofc but it seems to fit for me

Edit: Apparently his sister confirmed this in a memoir she wrote called The Wild Truth. There's an interesting article on the NPR website about it:

She and her brother Chris grew up with a volatile, viciously abusive father who made their weak-willed yet hyper-competent mother both his victim and his accomplice.

This is a really similar situation to mine. Took many years of therapy to get to where I am, but I'll probably never really fully heal from it.